exists and is an alternate of . Since this is regarding statistics I assume you mean lower case sigma (Ï) which, in statistics, is the symbol used for standard deviation, and Ï2 is known as the variance.
The Acceptable Quality Limit, commonly referred to as AQL, is a method widely used to measure a production order sample to find whether or not the entire product order has met the client's specifications. The customer then has the data to make an informed decision to accept or reject the lot.
The LOQ may be drastically different between laboratories so another detection limit is commonly used that is referred to as the Practical Quantification Limit (PQL). IUPAC, Compendium of Chemical Terminology, 2nd ed. (the Gold Book) (1997).